"Perfectly hydrophobic" surfaces have been developed by McCarthy and are being applied to low friction motion and lubrication McCarthy and Crosby. Shown in the image is an "18-wheel vehicle", prepared by treating a dimethyldichlorosilane-treated quartz plate with UV/ozone through a mask containing 18 hexagonally arrayed 1 mm diameter holes spaced by 4 mm on center. Emersion of this substrate in water, followed by removal normal to the water surface, produces 18 sessile droplets on the hydrophilic spots. This plate slides effortlessly on perfectly hydrophobic surfaces and accelerates on surfaces inclined by as little as 1° from the horizontal. These findings have significant ramifications for microfluidic devices, solid material transport, and self-cleaning surface applications.
